EP3781897B1 - Method and thz measuring device for measuring a measurement object using electromagnetic radiation - Google Patents

Description

The invention relates to a method for measuring a measurement object with electromagnetic radiation, and a corresponding measuring device.

THz measuring devices for measuring distances and layer thicknesses emit THz radiation, e.g. B. in the frequency range from 0.01 to 10 THz and can detect THz radiation reflected on measurement objects. Thus, distances from interfaces to the THz measuring device z. B. can be detected directly as runtime measurements or with a frequency modulation as a frequency shift. The spectral range thus also extends into the millimeter wave range.

This allows z. B. the plastic pipes are measured directly after their extrusion in order to detect irregularities in the layer thickness without contact. The THz radiation is partially reflected at the boundary surfaces, since the material of the measurement objects, e.g. B. plastic has a higher refractive index than the surrounding air.

The resolution of the THz measuring devices depends on their physical measuring principle and the modulation. Optical measuring devices, e.g. B. by means of short-time lasers and thereby stimulated transmitting and receiving antennas enable broadband measurements and high resolutions of the layer thicknesses. However, they are correspondingly complex and expensive in terms of equipment. Fully electronic THz measuring devices generally have transmit and receive dipoles that emit and receive the THz radiation; they are often operated in frequency modulation or as pulsed radiation. Higher resolutions for detecting small distances often require high bandwidths for the frequency ranges used. However, such high bandwidths can in turn disrupt other processes in which data communication or investigations take place in predetermined frequency ranges. In general, open investigations with undirected, freely escaping radiation without external shielding are limited to specified frequency ranges, eg ISM ranges (industrial, scientific, medical), unless shielding or external encapsulation, eg by an outer housing, can be proven.

US2015/060673A1 shows a system and method for determining anomalies hidden in a person. For this purpose, a detection probe is provided with an electromagnetic transmitter and an electromagnetic receiver. The electromagnetic transmitter emits electromagnetic pulses and the receiver correspondingly receives electromagnetic pulses within an appropriate waveform window at specific points in time. The electromagnetic pulses are within the terahertz spectral range of 0.04 to 4 THz. The transmitter and the receiver can be provided in a portable measuring sonde.

US2015/0212060A1 shows a coating device for applying a layer to a body, a sensor system being provided for characterizing a coating of the body. Sensing is contactless using THz radiation. Radiation from a light source is guided via a radiation cable to a THz transmitter and from there it is emitted onto the body to be examined.

The item " WARP portable - the innovative hand-held measuring device for wall thickness and diameter measurement of plastic pipes", Extrusion, June 1, 2017 (2017-06-01), pages 24-25, XP055598027 describes a handheld gauge that can be grasped by a user and applied to plastic tubing to measure wall thickness and inside and outside diameters.

The invention is based on the object of creating a method for THz measurement of test objects and a THz measuring device that enable reliable measurement of test objects, in particular layer thickness measurements of e.g. tubular or cylindrical test objects, with little effort.

This task is solved by a THz measuring method and a THz measuring device according to the independent claims. The dependent claims describe preferred developments.

The THz measuring device according to the invention is intended in particular for carrying out a THz measuring method according to the invention; the method according to the invention can be carried out in particular with the THz measuring device according to the invention.

The phases of a preliminary measurement and a main measurement are planned here. The pre-measurement is used to detect a measurement object and determine the distance of the measurement object from the THz measuring device or from its THz transceiver. In the preliminary measurement, it is determined in particular whether the determined distance of the measurement object or its outer boundary surface falls below a limit distance.

• Ermitteln, ob ein Messobjekt erfasst ist,
• falls das Messobjekt erfasst ist, Ermitteln eines aktuellen Abstandes des THz-Messgeräts oder des THz-Transceivers von der Grenzfläche,
• Vergleichen des ermittelten aktuellen Abstandes mit einem Grenzabstand, und
• bei Unterschreiten des Grenzabstandes nachfolgend Einleiten einer Hauptmessung oder Anzeigen einer Einleitung der Hauptmessung.

The pre-measurement phase thus has the steps

• Determining whether a measurement object is detected
• if the measurement object is detected, determining a current distance of the THz measuring device or the THz transceiver from the interface,
• comparing the determined current distance with a limit distance, and
• if the limit distance is not reached, a main measurement is subsequently initiated or an initiation of the main measurement is displayed.

If a measurement object is detected and it is also determined that the distance is below the limit, the main measurement is then initiated directly or the user is informed that he can initiate the main measurement.

In the main measurement, a measurement is then carried out with a main measurement THz transmission beam with a main measurement bandwidth. In the main measurement, the layer thickness, e.g. B. a wall thickness of a plastic pipe, determined very precisely. In addition or as an alternative to a wall thickness measurement, however, other measurements of the geometric relationships or spectroscopic examinations or analyzes can also be carried out.

According to a preferred embodiment, a first THz transmission beam with a smaller first bandwidth is initially emitted in the preliminary measurement. In the main measurement, the measurement then takes place with the main measurement THz transmission beam, which thus represents a second THz transmission beam, with the main measurement bandwidth, which thus represents a second bandwidth, with the second bandwidth or main measurement bandwidth being greater than the first bandwidth is.

In the pre-measurement phase, the THz measuring device may be further away from the measurement object, so that the THz radiation emitted bypasses the measurement object and gets into the environment may have negative effects. Thus, according to the invention, it is preferably provided to limit the bandwidth in this phase of the preliminary measurement, since only an at least rough determination of the distance is required for the detection of the measurement object; it is generally sufficient to estimate that the limit distance has not been reached.

If it is determined that the distance is below the limit, the THz radiation emitted by the THz measuring device cannot bypass the measuring object and cause direct negative effects in the environment; Rather, the THz radiation is radiated into the measurement object with a high level of certainty and is reflected and/or scattered or also absorbed in it. Therefore, in the phase of the main measurement, the larger second bandwidth can be selected, which enables a higher resolution and, in particular, a more accurate determination of the layer thickness.

In the pre-measurement phase, with a fully electronic measuring device, e.g. B. a bandwidth of 1 GHz can be selected; in the phase of the main measurement, a higher bandwidth of e.g. 20, 30 or 40 GHz, but also significantly higher, e.g. 1000 GHz or more can be selected.

The frequency of the THz radiation can be in the frequency range from 0.01 to 10 THz, both in the measuring device and in the method.

The wavelength range of the THz radiation can thus be referred to as terahertz radiation, microwave radiation or also radar radiation.

Thus, according to the invention z. For example, measurements with a high bandwidth are also possible without external shielding. On the one hand, there is an expansion of bandwidth possible; a frequency range of a narrow-band ISM range can be selected in the preliminary measurement phase, and then in the main measurement a broader frequency range around the frequencies of the first measurement. However, other frequency ranges can also be selected in the main measurement, for example other broadband frequency ranges. In addition or as an alternative, the power or intensity in the phase of the main measurement can also be increased.

According to a preferred embodiment, the method according to the invention is designed in such a way that the phases or a part of the phases are displayed on a display device and/or are output by an optical display device, in particular as an optical signal.

According to a preferred embodiment, the method according to the invention is further developed such that in the phase of the main measurement when measuring the measurement object with the main measurement THz transmission beam, a measurement of geometric properties takes place, in particular a layer thickness between boundary surfaces of the measurement object is determined.

According to a preferred embodiment, the THz measuring device according to the invention is developed in such a way that it has an output device for the acoustic or optical output or display of the phases, in particular the pre-measurement for correcting the positioning by the user.

According to a preferred embodiment, the THz measuring device according to the invention is further developed such that it is self-sufficient or connected to a stationary unit wirelessly or via a flexible data and power supply for handling and for setting the distance by the user.

According to the invention, a portable measuring device can be used in particular, which the user can thus freely handle and position in the preliminary measurement phase. As soon as the user has positioned the measuring device correctly, e.g. vertically on the boundary surfaces of the measuring object and below the limit distance, this is recognized and displayed by the control device or the main measurement is carried out directly.

• Phase einer Vormessung (I), in der ein erster THz-Sendestrahl eines THz-Transceivers eines THz-Messgeräts in einem ersten Frequenzbereich und mit einer ersten Bandbreite entlang einer optischen Achse auf das Messobjekt ausgestrahlt wird und von einer Grenzfläche des Messobjektes reflektierte THz-Strahlung detektiert wird (Schritt St3),
• Ermitteln, ob ein Messobjekt erfasst ist (Schritt St4),
• falls das Messobjekt erfasst ist, Ermitteln eines aktuellen Abstandes des THz-Messgeräts oder des THz-Transceivers von der Grenzfläche (Schritt St5),
• Vergleichen des ermittelten aktuellen Abstandes mit einem Grenzabstand (Schritt St6), und
• bei Unterschreiten des Grenzabstandes (Schritt St8) nachfolgend Einleiten einer Hauptmessung (II) oder Anzeigen einer Einleitung der Hauptmessung (II),
• Phase der Hauptmessung (II), in der ein zweiter THz-Sendestrahl mit einer zweiten Brandbreite, die größer als die erste Bandbreite ist, entlang der optischen Achse auf das Messobjekt eingestrahlt wird und reflektierte THz-Strahlung detektiert wird (Schritt St9),

wobei mit dem ausgesandten zweiten THz-Sendestrahl und der detektierten reflektierten THz-Strahlung eine Vermessung von geometrischen Eigenschaften oder Materialeigenschaften des Messobjektes erfolgt (Schritt St10),

• Ausgeben des Messergebnisses (Schritt St11).

Thus, according to this preferred embodiment, the method for THz measurement of a measurement object has at least the following steps:

• Phase of a preliminary measurement (I), in which a first THz transmission beam of a THz transceiver of a THz measuring device is emitted in a first frequency range and with a first bandwidth along an optical axis onto the measurement object and THz radiation reflected from an interface of the measurement object is detected (step St3),
• determining whether a measurement object is detected (step St4),
• if the measurement object is detected, determining a current distance of the THz measuring device or the THz transceiver from the interface (step St5),
• Comparing the determined current distance with a limit distance (step St6), and
• if the limit distance is not reached (step St8), a main measurement (II) is then initiated or an initiation of the main measurement (II) is displayed,
• Phase of the main measurement (II), in which a second THz transmission beam with a second bandwidth that is larger than the first bandwidth is radiated onto the measurement object along the optical axis and reflected THz radiation is detected (step St9),

with the emitted second THz transmission beam and the detected reflected THz radiation being used to measure geometric properties or material properties of the measurement object (step St10),

• outputting the measurement result (step St11).

• THz-Messgerät zur Vermessung eines Messobjektes,
• wobei das THz-Messgerät aufweist:
  • einen THz-Transceiver zum Aussenden von THz-Strahlung entlang einer optischen Achse und Empfang reflektierter THz-Strahlung,
  • eine Steuereinrichtung zur Aufnahme von Messsignalen des THz-Transceivers und Ermitteln eines Abstandes und eines Messergebnisses des Messobjektes, und
  • eine Ausgabeeinrichtung zur Ausgabe eines Messergebnisses,
  • dadurch gekennzeichnet, dass
  • das THz-Messgerät tragbar ist und einen Griffbereich zum Erfassen und
  • Hantieren durch einen Benutzer aufweist,
  • wobei die Steuereinrichtung ausgelegt ist,
  • in einer Phase der Vormessung die THz-Messstrahlung als ersten THz-Sendestrahl entlang der optischen Achse mit einer ersten Bandbreite auszusenden und in einer Phase der Hauptmessung (II) als zweiten THz-Sendestrahl mit einer zweiten Bandbreite auszusenden, die größer als die erste Bandbreite ist, für eine höhere Auflösung,
  • wobei die Steuereinrichtung in der Vormessung (I) ermittelt, ob ein Messobjekt erfasst und falls das Messobjekt erfasst ist, den Abstand des THz-Messgeräts oder des THz-Transceivers von einer Grenzfläche des Messobjektes ermittelt und mit einem Grenzabstand vergleicht und in Abhängigkeit des Vergleichs bei Unterschreiten des Grenzabstandes eine Hauptmessung (II) einleitet oder anzeigt,
  • und wobei die Steuereinrichtung ausgelegt ist, in der Hauptmessung (II) Messeigenschaften des Messobjektes zu ermitteln.

According to the preferred embodiment, the measuring device has the following features:

• THz measuring device for measuring a measurement object,
• where the THz meter has:
  • a THz transceiver for emitting THz radiation along an optical axis and receiving reflected THz radiation,
  • a control device for recording measurement signals from the THz transceiver and determining a distance and a measurement result of the measurement object, and
  • an output device for outputting a measurement result,
  • characterized in that
  • the THz meter is portable and has a grip area for sensing and
  • has handling by a user,
  • wherein the control device is designed
  • to emit the THz measurement radiation as a first THz transmission beam along the optical axis with a first bandwidth in a phase of the preliminary measurement and to emit a second THz transmission beam with a second bandwidth in a phase of the main measurement (II) that is larger than the first bandwidth , for higher resolution,
  • wherein the control device determines in the preliminary measurement (I) whether a measurement object is detected and, if the measurement object is detected, determines the distance of the THz measuring device or the THz transceiver from an interface of the measurement object and compares it with a limit distance and, depending on the comparison Falling below the limit distance initiates or indicates a main measurement (II),
  • and wherein the control device is designed to determine measurement properties of the measurement object in the main measurement (II).

• eine Laser-Abstandssensor-Einrichtung, die den Abstand z.B. durch Triangulation ermittelt, oder auch
• einen Ultraschallsensor, der den Abstand mittels Ausgabe eines Ultraschall-Sendesignals und Aufnahme eines Ultraschal-Reflexionssignals ermittelt,
• oder auch einen Kontakt-Sensor, der z.B. etwas vorsteht und als Taster bei Kontakt mit dem Messobjekt eingedrückt wird.

In a non-claimed alternative to this embodiment with a pre-measurement with a measurement with a smaller bandwidth, however, the pre-measurement can also be carried out by an additional sensor, eg

• a laser distance sensor device that determines the distance for example by triangulation, or
• an ultrasonic sensor that determines the distance by outputting an ultrasonic transmission signal and recording an ultrasonic reflection signal,
• or a contact sensor that, for example, protrudes slightly and is pressed as a button when it comes into contact with the measurement object.

• eine Suchphase, bis das Messobjekt erfasst ist; in der Suchphase wird somit z.B. noch keine reflektierte THz-Strahlung detektiert, da der Abstand zu groß oder die Grenzflächen nicht senkrecht zur ausgesandten THZ-Strahlung liegen;
• eine Erfassungsphase, in der das Messobjekt erfasst ist, aber der Grenzabstand noch nicht erreicht ist und/oder der Winkel der optischen Achse noch nicht hinreichend senkrecht zu den Grenzflächen liegt.

The pre-measurement phase can also be subdivided into

• a search phase until the measurement object is detected; in the search phase, for example, no reflected THz radiation is detected yet because the distance is too great or the boundary surfaces are not perpendicular to the emitted THz radiation;
• a detection phase in which the measurement object is detected but the limit distance has not yet been reached and/or the angle of the optical axis is not yet sufficiently perpendicular to the interfaces.

In the preliminary measurement phase, a measurement can be carried out continuously; in the phase of the main measurement can also z. B. only occasionally a measurement, e.g. a distance or layer thickness measurement.

The phases and/or results can be presented to the user continuously, e.g. B. on a visual display device or acoustically. For example, the user can grasp the measuring device by its gripping area, align it with the measurement object and start the pre-measurement phase by pressing an actuating device. Here, for example, the search phase can first be displayed to him, so that he knows that the measuring device is not held correctly or is not positioned precisely or too far. Thus, when the acquisition phase is displayed, the user will position the measuring device even more precisely or closer until the measurement phase is displayed and/or already begins.

For example, the user can B. in the case of a portable measuring device with a suitable contact surface along the measuring object and carry out continuous measurements; if he temporarily holds the portable measuring device inaccurately or falls off the surface, e.g. B. by tilting the measuring device, since it may not follow the surface contour precisely when driving along the round surface, this is immediately displayed to the user, e.g. B. by a red display for the pre-measurement phase. The user can then position the measuring device more precisely and continue the main measurement.

In this case, the portable measuring device can have a contact contour, in particular on its front end region, advantageously on a scattering screen. Thus, the scattering screen keeps interfering THz radiation away from the THz transceiver, and also serves with contour lines for precise positioning on the measurement object. Here z. B. pairs of contour lines are present, which allow suitable positioning of measurement objects with defined curvatures, such as plastic pipes with defined diameters. Thus, several pairs of contour lines on the front side of the shaped panel can be used for precise installation; as soon as the user tilts the portable measuring device, it is displayed to the user as the phase of the pre-measurement because the reflected THz beam does not return or the distance becomes too large.

Thus, even with a portable measuring device, easy handling by the user and precise measurements, in particular also very precise layer thickness measurements, are possible without great effort.

Fig. 1

eine perspektivische Ansicht einer Messanordnung mit einem tragbaren THz-Messgerät in der Phase der Vormessung;

Fig. 2

eine Messanordnung mit einem tragbaren THz-Messgerät in der Phase der Hauptmessung;

Fig. 3

ein Blockschaltbild der Messanordnung, und

Fig. 4

ein Flussdiagramm des THz-Messverfahrens gemäß einer Ausführungsform.

The invention is explained in more detail below with reference to the accompanying drawings of some embodiments. Show it:

1

a perspective view of a measuring arrangement with a portable THz measuring device in the preliminary measurement phase;

2

a measuring arrangement with a portable THz measuring device in the phase of the main measurement;

3

a block diagram of the measuring arrangement, and

4

a flow chart of the THz measurement method according to an embodiment.

A THz measurement arrangement 1 has according to the embodiments of Figures 1 and 2 a portable THz measuring device 2 for measuring a measurement object 3, e.g. B. a plastic tube. The portable THz meter 2 is in Figures 1 and 2 shown as an example in different configurations.

The portable THz measuring device 2 has a handle area 4 for the user to grip and handle, and a front end area 5 which is preferably a contact area with a shaped panel 25 . The portable THz meter 2 can according to 1 e.g. B. angled, or according to the embodiment of 2 also be elongate or rod-shaped. Furthermore, the portable THz meter 2 according to the embodiment of FIG 2 be fully portable, with no data connection to a stationary unit, or so 1 be connected via a data and power supply line 6 to a stationary facility. Also can eg a portable unit such as those in 2 is shown, e.g. B. wirelessly transmit data to a stationary unit.

According to the block diagram 3 the portable THz measuring device 2 has a transmitting and receiving device 8, ie a transmitting and receiving dipole or transceiver 8, which is preferably fully electronic, ie designed as a transmitting and receiving dipole and is controlled by an electronic control unit 10. The transmitting and receiving device 8 emits an electromagnetic beam 12, hereinafter referred to as THz transmission beam 12, in a radiation cone 12a along an optical axis A, in particular in the frequency range from 0.01 to 10 THz, ie 10 GHz to 10 THz, in particular as a pulsed THz radiation or in frequency modulation. If it strikes an outer surface 3a and inner surface 3bd of the measurement object 3 at an orthogonal angle, THz radiation 14 is reflected back along the optical axis A to the transmitting and receiving device 8 and detected there. A propagation time of the THz radiation from the transmitting and receiving device to the boundary surface 3a and back can thus be detected, which can be determined and converted directly or, with frequency modulation, also in the frequency space (by means of Fourier transformation). Thus, from the THz measurement of the transmitting and receiving device 8 by the electronic control device 10, a distance d of the transmitting and receiving device 8 to the interface 3a can be determined.

In a preliminary measurement I, the THz transceiver 8 emits a first THz transmission beam 112 along the optical axis A, which is in a narrow frequency band fb1 with a bandwidth b1 of z. B. 1 GHz is formed. In this preliminary measurement I, in particular in a search phase la, it can first be determined whether a measurement object 3 or an essentially orthogonal boundary surface 3a of the measurement object 3 can be detected with the measurement in the measurement and subsequently in a determination phase Ib whether the current measurement distance d is below a limit distance d_tres or not. If d<d_tres, it is recognized that there is a permissible distance for a subsequent main measurement II, and the main measurement II is initiated directly or an indication signal is output again that the main measurement can be carried out subsequently.

In the main measurement II, a THz transmission beam 212 is in a second, broader frequency band fb2, z. B. with bandwidth b2 of e.g. 20, 30 or 40 or also 1000 GHz, since the emitted THz beam 212 hits the measurement object 3 and is thus damped or weakened by the material of the measurement object 3, in particular by reflections and possibly also absorption. In the main measurement, a layer thickness d3, for example, is then determined as the distance between the outer surface 3a and the inner surface 3b of the measurement object 3; Correspondingly, other layer thicknesses can also be determined, especially in the case of multi-layer pipes. In addition or as an alternative to this, other geometric distances or structures can also be measured; In addition or as an alternative to this, spectroscopic measurements can also be carried out, in which e.g. the absorption behavior of the measurement object 3 is examined, e.g. in spatial resolution.

The electronic control unit 10 can advantageously output output signals S2 to an output device 16, the output device 16 z. B. can be an optical or acoustic display device and indicates the different phases Ia, Ib, II or states. This can, for example, be displayed in three different display fields or by different displays on a common display field.

Furthermore, the results are preferably evaluated and compared with target values, so that the portable measuring device 2 or its Output device 16 is also displayed qualitatively, whether z. B. too small a layer thickness has been determined or the measurement result is generally displayed on the output device 16 . In the case of spectroscopic investigations, for example, it can be indicated whether specific substances, for example specific chemical compounds, have been detected.

The limit distance d_tres can in particular be matched to the length of a shaped panel 25 of the front end area 5; so the shaped panel 25 z. B. have two investment contour lines 25a, 25b, which come into contact with the surface 3a of the measurement object 3 in the correct position. If a sufficient measurement signal is determined in the pre-measurement I phase, i.e. the amplitude of the measurement signal exceeds a limit value, and the measurement position is therefore vertical, and the determined distance d is still below the limit distance d_tres, a correct system can also be used without touch sensors, etc. , i.e. can be determined solely by the distance measurement, so that the phase of the main measurement II is then initiated.

In the pre-measurement I phase, a measurement can be carried out within a standard range or within an allocated measurement range for such a THz distance measurement, i. H. in particular within an ISM band (Industrial Scientific and Medical) in which measurement is also permitted without shielding or attenuation, e.g. at 24 GHz to 24.25 GHz or 122 to 123 GHz or 244 to 126 GHz.

Thus, the portable measuring device 2 in the pre-measurement phase I z. B. an ISM band is maintained, whereupon a higher bandwidth is then set in the phase of the main measurement II, for a higher resolution or, for example, a more precise detection of the layer thickness or a precise spectroscopic examination.

At the THz measuring device 2, e.g. B. in the grip area 4, an actuator 18 z. B. be provided as a push button or switch, with which the user thus initiates the measurement. 4 shows an example of a measurement method according to an embodiment of the invention:
After starting in step St0, the user grasps the grip area 4 in step St1 and guides the measuring device 2 in the direction of the measurement object 3.

To initiate the phase of the preliminary measurement I, the user thus actuates the actuating device 18 in step St2 and outputs an actuating signal S1 or switch-on signal,
so that the control device 10 subsequently outputs control signals S2 to the THz transceiver 8 in step St3 and initially a preliminary measurement I, in particular a search phase Ia, starts with the first THz transmission beam 112 with a smaller bandwidth b1, with the THz transceiver 8 generating measurement signals S3 .

• in Schritt St4, ob bereits ein Messobjekt 3 erfasst ist (Suchphase Ia)
• in Schritt St5, falls bereits das Messobjekt 3 bzw. dessen Grenzfläche 3a erfasst ist, den aktuellen Abstand d und
• in Schritt St6, ob der aktuelle Abstand d oberhalb des Grenzabstandes d_tres liegt (Erfassungsphase Ib).

und zeigt die ermittelte Phase durch Anzeigesignale S3 an einer Anzeigeeinrichtung 16 an. Hierbei kann auch z.B. das Messsignal auf einer Skala für den Messabstand d angezeigt werden.The control device 10 records the measurement signals S3 and determines

• in step St4 whether a measurement object 3 has already been detected (search phase Ia)
• in step St5, if the measurement object 3 or its boundary surface 3a has already been detected, the current distance d and
• in step St6 whether the current distance d is above the limit distance d_tres (detection phase Ib).

and displays the determined phase on a display device 16 by display signals S3. Here, for example, the measurement signal can also be displayed on a scale for the measurement distance d.

• so dass in Schritt St8 die Steuereinrichtung 10 erkennt, dass der aktuelle Abstand d unterhalb des Grenzabstandes d_tres liegt und
• in Schritt St9 direkt die Hauptmessung II beginnt, oder dem Benutzer angezeigt wird, dass er über die Betätigungseinrichtung 18 nachfolgend eine Hauptmessung II einleiten kann.

The user thus knows that he may have to position the measuring device 2 closer to the measurement object 3 or, for example, that the measuring device 2 is tilted. In step St7, the user thus guides the portable THz measuring device 2 sufficiently close and properly to the test object 3, e.g. B. until the shaped screen 25 or the contour lines 25a, 25b come into complete contact with the outer surface 3a,

• so that in step St8 the control device 10 recognizes that the current distance d is below the limit distance d_tres and
• the main measurement II starts directly in step St9, or the user is informed that he can subsequently initiate a main measurement II via the actuating device 18.

In the main measurement II, in step St10, the second THz transmission beam 212 with a larger bandwidth carries out a more detailed examination, e.g. an exact determination of the layer thickness d3 or another geometric property or e.g. a precise spectroscopic examination, which is output in step St11, e.g the display device 16.

In addition to measurements of layer thicknesses or wall thicknesses, general structural examinations or examinations of the geometric structure can also be carried out, as well as spectroscopic examinations in which, for example, chemical substances are recorded on the basis of their spectroscopic absorption behavior.

Reference List

1

THz measurement setup

2

portable THz meter

3

Measurement object, e.g. plastic pipe

3a

Outer surface of the measurement object 3

3b

Inner surface of the measurement object 3

4

grip area

5

front end area, preferably contact area

8th

THz transceiver, e.g. transmit and receive dipole

10

electronic control device

12

THz transmit beam

12a

emission cone

112

first THz transmission beam of the preliminary measurement

212

second THz transmission beam of the main measurement, i.e. main measurement transmission beam

14

reflected THz radiation

16

output device

18

actuating device

25

Molded panel of the front end area 5

25a, 25b

plant contour lines

A

optical axis

b1

first, smaller range of z. B. 1 GHz, narrower first frequency band, the preliminary measurement

b2

second, larger bandwidth z. B. 20, 30 or 40 GHz, wider second frequency band, the main measurement

i.e

Distance of the THz transceiver 8 to the interface 3a

d_tres

limit distance

d3

layer thickness

e1

first display, eg for search phase Ia

e2

second display, e.g. for acquisition phase Ib

I

Pre-measurement phase

yes

Search phase for detecting the measurement object 3

Ib

acquisition phase

II

phase of the main measurement

S1

actuation signal

S2

control signal

S3

measurement signal

S4

Output signals to output device 16

St1 to St11

steps of the procedure

Claims (13)

1. Method for THz measuring a measurement object (3),

   comprising at least the following steps:

   - phase of a pre-measurement (I) (St3),

   - determining whether a measurement object (3) has been detected (St4),

   - if the measurement object (3) has been detected, determining a current distance (d) of a THz measuring device (2) or a THz transceiver (8) from a boundary surface (3a) of the measurement object (St5),

   - comparing the determined current distance (d) with a distance limit (d_tres) (St6), and

   - if the distance limit (d_tres) has not been exceeded (St8), subsequently initiating a main measurement (II) or indicating the initiation of the main measurement (II),

   - phase of the main measurement (II) in which a main measurement THz transmission beam (212) having a main measurement bandwidth (b2) is emitted along an optical axis (A) towards the measurement object (3) and reflected THz radiation (14) is detected (St9), whereby, using the emitted main measurement THz transmission beam (212) and the detected reflected THz radiation (14), a measurement of geometric characteristics or material characteristics of the measurement object (3) is carried out (St10),

   - putting out the measurement result (St11),

   characterised in that

   in the phase of pre-measurement (I) a first THz transmission beam (112) of the THz transceiver (8) of the THz measuring device (2) is emitted, in a first frequency range (fb1) and having a first bandwidth (b1), along the optical axis (A) towards the measurement object (3) and THz radiation reflected off of the boundary surface (3a) of the measurement object (3) is detected (St3), and

   in the phase of main measurement (II) the main measurement transmission beam (212) is emitted as second transmission beam (212),

   whereby the main measurement bandwidth (b2) of the main measurement transmission beam (212) is larger than the first bandwidth (b1),

   where the THz radiation (12, 112, 212) lies in a frequency range between 0.01 and 10 THz.
2. Method according to claim 1, characterised in that the measuring device (2) is portable and held and handled by a grip region (4), whereby it is being positioned such that the front end region (5) is in front of or on the measurement object (3) (St1, St7).
3. Method according to claim 2, characterised in that said portable THz measuring device (2) is placed by the user by a contact surface formed at the front end region (5), preferably a shaped panel (25), against a boundary surface (3a) of the measurement object (3) so as to not exceed the distance limit (d_tres).
4. Method according to one of the above claims, characterised in that in the phase of main measurement (II), when measuring the measurement object (3) using the main measurement THz transmission beam (212), a layer thickness (d3) between boundary surfaces (3a, 3b) of the measurement object (3) is determined.
5. Method according to one of the above claims, characterised in that in the phase of main measurement (II), when measuring the measurement object (3) using the main measurement THz transmission beam (212), a material analysis of the measurement object (3) is carried out, in particular a spectroscopic analysis, e.g. a spatially resolved spectroscopic analysis of the measurement object (3).
6. Method according to one of the above claims, characterised in that the phase of main measurement (II) is initiated automatically upon determination that the distance limit (d_tres) has not been exceeded (St9).
7. Method according to one of the above claims, characterised in that in the phase of pre-measurement (I) the THz transmission beam (112) is emitted continuously for continuous detection of measuring objects and comparison of a current measuring distance (d) to the distance limit (d_tres).
8. Method according to one of the above claims, characterised in that in the phase of main measurement (II) another frequency range is emitted than the one in the phase of pre-measurement (i).
9. Method according to one of the above claims, characterised in that in the phase of main measurement (II) another intensity is emitted than the one in the phase of pre-measurement (i).
10. THz measuring device (2) for measuring a measurement object (3), said THz measuring device (2) comprising:

    a THz transceiver (8) for emitting THz radiation (12) along an optical axis (A) and receiving reflected THz radiation (14),

    a controller device (10) for collecting measurement signals (1) of the THz transceiver (8) and determining a distance (d) and a measurement result (d3) of the measurement object (3), and

    an output device (16) for putting out a measurement result,

    characterised in that

    said THz measuring device (8) is portable and comprises a grip region (4) for being grabbed and handled by a user,

    said controller device (10) being configured for a phase of pre-measurement (I) and a phase of main measurement (II),

    said controller device (10) being configured to emit, in the phase of main measurement (II), a main measurement THz transmission beam (212) having a main measurement bandwidth (b2) along the optical axis (A),

    said controller device (10) determining in the pre-measurement (I) whether a measurement object has been detected and, if the measurement object has been detected, determining the distance (d) of the THz measuring devices (2) or the THz transceiver (8) from a boundary surface (3a) of the measurement object (3) and comparing the same with a distance limit (d_tres) and, depending on the comparison, initiates or indicates the main measurement (II) when the distance limit (d_tres) has not been exceeded,

    and said controller device (10) being configured to determine measurement characteristics of the measurement object in the main measurement (II),

    characterised in that

    said measuring device (2) is configured to emit, in the phase of pre-measurement (I), the THz radiation (12) as a first THz transmission beam (112) along the optical axis (A) with a first bandwidth (b1),

    and to emit, in the phase of main measurement (II), the main measurement THz transmission beam (212) as a second THz transmission beam (212) with the main measurement bandwidth (b2) along the optical axis (A),

    the main measurement bandwidth (b2) being larger than the first bandwidth (b1), for a higher resolution.
11. THz measuring device (2) according to claim 10, characterised in that the controller device (10) is configured to determine, in the main measurement (II), geometric characteristics and/or material characteristics of the measurement object, e.g. the layer thickness (d3) as the distance between two boundary surfaces (3a, 3b) and/or material characteristics by means of spectroscopic analysis.
12. THz measuring device (2) according one of the claims 10 or 11, characterised in that it comprises a shaped panel (25) at its front end region (5) having contour lines (25a, 25b), in particular pairs or arc-shaped contour lines, for being placed in contact with the exterior surface (3a) of the measurement object, in particular a pipe (3), whereby, when the contour lines (25a, 25b) are in contact with the exterior surface (3a) of the measurement object (3), the current distance (d) is below the distance limit (d_tres).
13. THz measuring device (2) according to one of the claims 10 through 12, characterised in that THz transceiver (8) is designed to be fully electronic, in particular as a transmitter and receiver dipole, e.g. using frequency modulation or pulsed radiation,
    where, in main measurement (II) using the wider main measurement bandwidth (b2), a higher resolution of the measurement result can be generated so as to make a more precise determination of measured characteristics of the measurement object, e.g. a layer thickness (d3) or spectroscopic analysis.

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